There is a detecting element with an organic semiconductor layer which converts radiations into electrical charges. The detecting element outputs a current signal and the magnitude of the current signal is proportional to the number of the electron-hole pairs generated by a radiation incident on the organic conversion layer. In order to deposit the energy of the radiation efficiently, the thick conversion layer is generally suitable.
However, as the conversion layer becomes thicker, the difference in the contribution of holes and electrons to the output signal becomes larger because electrons move to an electrode longer than holes in the conversion layer. As a result, the output signals not only become dependent on the number of electron-hole pairs but also become positionally-dependent on the positions of generation of electron-hole pairs in the organic semiconductor layer. For that reason, in the conventional technology, there are times when the sensitivity for detection undergoes a decline.